As memories of next and subsequent generations, Magnetoresistive Random Access Memory (MRAM) is examined. MRAM stores data using Tunneling Magneto-Resistance Effect.
MRAM has plural Magnetic Tunnel Junction (MTJ) elements disposed in a matrix state. Each MTJ element has a layered structure composed of two magnetic layers interposed between a lower electrode and an upper electrode and a nonmagnetic layer sandwiched between the two magnetic layers.
Since the magnetic layers provided with the MTJ element have a low heat resistance, the characteristics of the MTJ element may be changed by the heat applied to the magnetic layers in a manufacturing process. Thus, in a process for manufacturing MRAM, after an MTJ element is formed, it is necessary to keep a process temperature to a predetermined temperature or less, for example, 500° C. or less so that the MTJ element is not degraded by heat.
Further, interlayer dielectric films are interposed between respective MTJ elements to electrically isolate the respective MTJ elements. The interlayer dielectric film is composed of, for example, a silicon dioxide films, and a method of using polysilazane (PSZ) is available as a method of forming the silicon dioxide film.
To describe the method of using PSZ in more detail, a PSZ solution is applied to the entire surface of a substrate on which an MTJ element is disposed, a solvent in the PSZ solution is volatilized by baking, and then the PSZ is heated to 600 to 650° C. using electromagnetic waves having a short wavelength, i.e., ultraviolet rays, visible light rays, infrared rays or the like under an atmosphere which contains oxygen or water vapor.